Three's Company: An additional non-transiting super-Earth in the bright HD 3167 system, and masses for all three planets

• Published in: arXiv.org 2017-06
• Main Authors: Christiansen, Jessie L, Vanderburg, Andrew, Burt, Jennifer, Fulton, B J, Batygin, Konstantin, Benneke, Björn, Brewer, John M, Charbonneau, David, Ciardi, David R, Andrew Collier Cameron, Coughlin, Jeffrey L, Crossfield, Ian J M, Dressing, Courtney, Greene, Thomas P, Howard, Andrew W, Latham, David W, Molinari, Emilio, Mortier, Annelies, Mullally, Fergal, Pepe, Francesco, Rice, Ken, Sinukoff, Evan, Sozzetti, Alessandro, Thompson, Susan E, Udry, Stéphane, Vogt, Steven S, Barman, Travis S, Batalha, Natasha E, Bouchy, Francois, Buchhave, Lars A, Butler, R Paul, Cosentino, Rosario, Dupuy, Trent J, Ehrenreich, David, Fiorenzano, Aldo, Hansen, Brad M S, Henning, Thomas, Hirsch, Lea, Holden, Bradford P, Isaacson, Howard T, Johnson, John A, Knutson, Heather A, Kosiarek, Molly, López-Morales, Mercedes, Lovis, Christophe, Malavolta, Luca, Mayor, Michel, Micela, Giuseppina, Motalebi, Fatemeh, Petigura, Erik, Phillips, David F, Piotto, Giampaolo, Rogers, Leslie A, Sasselov, Dimitar, Schlieder, Joshua E, Ségransan, Damien, Watson, Christopher A, Weiss, Lauren M
• Format: Article
• Language: English
• Subjects: Atmospheric composition; Extrasolar planets; Inclination; Planets; Radial velocity; Stability; Target detection; Thermal emission; Transit; Transits
• ISSN: 2331-8422
• DOI: 10.48550/arxiv.1706.01892

HD 3167 is a bright (V = 8.9), nearby K0 star observed by the NASA K2 mission (EPIC 220383386), hosting two small, short-period transiting planets. Here we present the results of a multi-site, multi-instrument radial velocity campaign to characterize the HD 3167 system. The masses of the transiting planets are 5.02+/-0.38 MEarth for HD 3167 b, a hot super-Earth with a likely rocky composition (rho_b = 5.60+2.15-1.43 g/cm^3), and 9.80+1.30-1.24 MEarth for HD 3167 c, a warm sub-Neptune with a likely substantial volatile complement (rho_c = 1.97+0.94-0.59 g/cm^3). We explore the possibility of atmospheric composition analysis and determine that planet c is amenable to transmission spectroscopy measurements, and planet b is a potential thermal emission target. We detect a third, non-transiting planet, HD 3167 d, with a period of 8.509+/-0.045 d (between planets b and c) and a minimum mass of 6.90+/-0.71 MEarth. We are able to constrain the mutual inclination of planet d with planets b and c: we rule out mutual inclinations below 1.3 degrees as we do not observe transits of planet d. From 1.3-40 degrees, there are viewing geometries invoking special nodal configurations which result in planet d not transiting some fraction of the time. From 40-60 degrees, Kozai-Lidov oscillations increase the system's instability, but it can remain stable for up to 100Myr. Above 60 degrees, the system is unstable. HD 3167 promises to be a fruitful system for further study and a preview of the many exciting systems expected from the upcoming NASA TESS mission.